DE 196 39 623 has disclosed a gas turbine for power generation having a compressor and an annular combustion chamber. A diffuser, which diverts the compressed air provided by the compressor at the annular compressor outlet in the direction of the burner arranged at the end side of the annular combustion chamber, is arranged between the compressor and the annular combustion chamber. For this purpose, the diffuser has flow-guiding contours as well as a metal diverter sheet which is C-shaped in cross section and is secured by a holder crossing the flow passage. Furthermore, a plurality of stationary removal tubes distributed over the circumference are arranged in the diffuser, coaxially with respect to the rotor, for removing cooling air, which removal tubes remove cooling air at the compressor outlet and pass it to the turbine stages of the gas turbine.
The holder for the C-shaped metal diverter sheet constitutes an obstacle blocking the flow passage formed by the diffuser. The arrangement of the removal tubes also interferes with the air which is flowing in the diffuser and is passed to the burners. This can give rise to flow losses. Furthermore, the tubes, which are distributed over the circumference, have to have a minimum diameter required to ensure that sufficient cooling air is provided for the turbine stages, so that not only the compressed air which flows out of the center of the compressor outlet but also the compressed air at the edge of the compressor outlet is removed.
Furthermore, FR2706533 has disclosed a diffuser for a turbomachine, in which a part-stream is removed in the diffuser in order to set a cabin pressure, to deice the body of the machine or to start the engine of an aircraft. A wedge-shaped distribution element, which initially divides the compressor end air flow into two part-streams, is arranged in the widening flow passage of the diffuser. Then, a third part-stream is removed from the inner part-stream through an opening arranged behind the tip of the distribution element. This third part-stream is routed outward through the hollow ribs which support the distribution element against the outer wall. The third part-stream removed in this way is then used for the above-mentioned purposes. In a further configuration, the diffuser which is known from FR2706533 has an inner and outer ribs supporting the distribution element. The inner ribs are in this case provided with an opening for decoupling the part-flow, through which opening the third part-flow that is to be decoupled can enter the cavity in the rib.
Since the part-flow removed in this way is used for deicing or, for example, to set the cabin pressure, the demands imposed on the air flow in terms of degree of contamination, pressure and temperature are relatively low.
By contrast, relatively high demands are imposed on the cooling air for the turbine blades and vanes of a stationary gas turbine, in order on the one hand to achieve a particularly high efficiency and on the other hand to avoid or reduce blockages or cross-sectional narrowings of impingement cooling openings or film cooling holes caused by particle deposits.